The most recent leap second was added on 2012 June 30:

The protocol files in this version have been updated to UTC1-TAI = -35.


The following IAU Circular describes prior leap seconds.


As announced by  the IAU Central Bureau for Astronomical Telegrams 
in Circular No. 9004 on 11 December 2008, Bulletin C36 of the
International Earth Rotation and Reference Systems Service announced that a
positive leap second will be added on 1 January 2009.  

From http://www.iers.org/products/16/11321/orig/bulletinc-036.txt --


     INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) 

SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE

SERVICE DE LA ROTATION TERRESTRE
OBSERVATOIRE DE PARIS                                   
61, Av. de l'Observatoire 75014 PARIS (France)
Tel.      : 33 (0) 1 40 51 22 26
FAX       : 33 (0) 1 40 51 22 91
e-mail    : services.iers@obspm.fr
http://hpiers.obspm.fr/eop-pc

                                              Paris, 4 July 2008
                                                           
                                              Bulletin C 36
                                
                                              To authorities responsible 
					      for the measurement and 
					      distribution of time                                         


                                   UTC TIME STEP
                            on the 1st of January 2009
                      

 A positive leap second will be introduced at the end of December 2008.
 The sequence of dates of the UTC second markers will be:		
		
                          2008 December 31,     23h 59m 59s
                          2008 December 31,     23h 59m 60s
                          2009 January   1,      0h  0m  0s
              
 The difference between UTC and the International Atomic Time TAI is:

  from 2006 January 1, 0h UTC, to 2009 January 1  0h UTC  : UTC-TAI = - 33s
  from 2009 January 1, 0h UTC, until further notice       : UTC-TAI = - 34s 
  
 Leap seconds can be introduced in UTC at the end of the months of December 
 or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every 
 six months, either to announce a time step in UTC or to confirm that there 
 will be no time step at the next possible date.
 


                                              Daniel GAMBIS
                                              Head		
                                              Earth Orientation Center of IERS
					      Observatoire de Paris, France